Pull latest docker image from prod for backend E2E testing

[ecurrencyhodler]

Context

Right now we are E2E testing the backend against the frontend main repo. We should be testing our E2E tests against production.

Our goal is to have auto-deployments of our backend straight to prod if all tests pass for CI/CD. That means that the backend for both staging and prod will be in sync.

However we will still need staging to test frontend updates such as testing layouts and design.

This also means that when working on an issue that requires both front and backend work, no frontend PR should ever be submitted before the backend issue has been deployed to prod. Otherwise, the frontend PR won't be tested against the appropriate backend updates in E2E testing.